As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to these users is an information handling system. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may vary with respect to the type of information handled; the methods for handling the information; the methods for processing, storing or communicating the information; the amount of information processed, stored, or communicated; and the speed and efficiency with which the information is processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include or comprise a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
Information handling systems, such as servers, may include more than one power supply unit (PSU). To meet high availability requirements, servers may deploy redundant PSUs such that, if a PSU fails, the remaining PSU(s) are able to provide enough power to continue system operation. In most cases, the redundant PSUs are hot swappable, allowing replacement without disruption to system operation. A typical redundancy mode for mainstream servers may be characterized as “1+1.” In that mode, a single PSU is able to supply enough power to supply the required power, while an identical PSU is provided for redundancy. Common practice has been to enable both PSUs to share the output load, with output rails “ORed” together via diodes or transistors, for example. In the general case, redundancy may be denoted as “M+N,” where M is the number of enabled PSUs required to meet a given system's power requirements, and N is the number of redundant PSUs available for handling failures.
PSUs require power for their own internal operation (commonly called “housekeeping”), typically on the order of Watts (W). Their basic power efficiency characteristics are such that a PSU is typically optimized for loads of approximately 50-100% of the PSU's maximum load rating, while efficiencies at lower loads are relatively poor. When multiple PSUs are enabled in parallel to support redundancy or loads greater than a single PSU can support, each PSU may end up running at a poor (e.g., less than 20%), or a sub-optimal (e.g., 20-40%), point. Thus, for power efficiency, it is desirable to turn off the redundant PSUs until an operational PSU fails. However, the challenges of that approach include ramping up the redundant PSU quickly and orderly enough in order to keep the system rails within the valid operating range.